Telephone transmitter



Filed Dec. 1923 fire/7f? liar/e5 ,6 4/00/12 lit Patented Feb. 28, 1928.

PAT Omari when a was. amtsmnmw aims; team we mam Emma CQM'BANY, raeearenaraa or raw YORK, R. R4 conroaa'rronor new max.

a pncaaba 6166 Deanne: 6, 1923. Serial N... 676,934.

. the two elements being so arranged and located with respect to each other that their response to the sound vibrations is s1multaneous, but opposite in effect.

In one embodiment of this invention thev two resistance varying elements are located in a cylindrical chamber connected with a transmitter mouthpiece, one of the resistance varying elements being provided with a diaphragm actuated by voice vibrations impinging dirctly upon it, the other being so arranged that the voice vibrations pass first tl'irough the resistance varying material before impinging upon the diaphragm.

In the drawings illustrating this invention.

Fig. 1 is a longitudinal sectional view through the casing, mouthpiece, and resistance varying elements Fig. 2 is a cross-sectional view taken upon line 2-2 of Fig. 1, and

Fig. 3 a diagrammatic representation of the circuit connections of the resistance varying elements.

As shown in the drawings, 5 designates a cylindrical casing of metal having an opening upon one side in which is secured the transmitter mouthpiece. Located in opposite ends of the cylindrical casing are a pair of resistance varying elements 7 and 8 which are alike in general, but differ in details as will be hereinafter pointed out.

The resistance varying elements are preferably of the type disclosed in the application of H. F. Dodge, Serial No. 525,898, filed December 30, 1921.

In the resistance varying element 7, a cylindrical shell 11 contains annular electrodes 9 and 10 separated by an annular insulating barrier 12. The annular electrode 9 is provided with a threaded flange 30 in which is inserted a disk 14 forming a closure for the element The electrode Sis insulatedfrom the cylindrical shell 1.1 by means of an inslilatrng washer '13 supported against the electrode 9 by ring 15 having threaded en gageinent with the shell 11. Theelc'ctrode 10 provided with an annular recess in which'is disposed the diaphragm 16 sup ported between banks of foil or. paper washers 17 by means of rili'g l8 in threaded engagement with the shell 11. A ring 19, having threaded flange engages the casing 5, to secure the element 7 in position. The surfaces of the diaphragm 16 and the disk 1 1 which are exposed to the granular material are preferably coated with an insulating compound.

The element 8 comprises a cylindrical shell 20 in which are supported annular electrodes 21 and 22 insulated from each other by means of the annular insulating barrier 12. The electrode 22 is insulated from the shell 20 by means of insulator 23 and is provided with an'annular recess in which the d1aphragm 16 is supported between the banks of washers 17 by a ring 32 in the same manner as in the case of the element 7. The shell 20 has an outwardly projecting flange 24: resting upon the edge of the casing 5 and clamped thereto by means of a threaded cup 26. The annular electrode 21 is provided with an annular recess wherein a screen or perforated wall 27 preferably of mercerized silk spans the opening in the electrode 21 and is secured thereto by a ring 28.

In the operation of the transmitter, the sound waves entering the chamber 31 act directly upon the diaphragm 16 of the resistance varying element 7 and, at the same time, pass through the perforated wall 27 and the granular material to actuate the diaphragm 16 and the resistance varying element- 8. The resistance in one element is, therefore, increased, while that in the other is decreased as in differential. type transmitters having a mechanical coupling between the microphone units.

The invention claimed is:

1. In a push-pull transmitter, a pair of microphonic elements each comprising a chamber containing resistance varying material, a closure for the front of one chamber pervious to air, a diaphragm forclosing the front of the other chamber, and a diaphra for the closure of the rear of the first mentioned chamber whereby the resistance in the two elements is varied simultaneously but with opposite effects through the impinging of sound Waves on each of said diaphragms.

2. In a push pull transmitter, a casing, a microphonic button therein comprising a carbon containing chamber and a diaphragm closure therefor adapted to respond directly to changes in pressure in the casing, a second microphonic button comprising a carbon containing chamber, a diaphragm closure therefor and an air pervious closure therefor directly opposed to the diaphragm closure of the first mentioned microphonic button, and adapted to permit the passage of air through the carbon containing chamber of the second button and against the diaphragm thereof, and means for directing sound Waves into said chamber.

3. In a push-pull transmitter, a pair of microphones acoustically coupled, each of said microphones comprising a chamber con taining a mass of carbon particles, a diaphragm closing the front of one microphone chamber, a second diaphragm'closing the rear of the other microphone chamber, and a member pervious to sound yibrations closing the front of said other chamber whereby said first diaphragm compresses the carbon mass in said first microphone chamber, and said second diaphragm loosens the carbon mass in said other microphone chamber through the impinging of sound waves on each of said diaphragms.

In Witness whereof, I hereunto subscribe my name this 3rd day of December, A. D

CHARLES R. MOORE. 

